[Redpiston]

I may have to do some suspension work on my 2+2. If I do, I thought I would make a stance adjustment while I'm in it. What I'm not sure of, should I lower the front or raise the rear. Attached is a photo of the car. I always thought it sat high in the front. My understanding is if I lower the front the rear will rise some. Im thinking I just need to get a shorter spring. Not comfortable with just cutting part of turn of a spring to make it shorter. Any advice is welcome.

[HWYSTR455]

It's true, lowering front will raise the rear, but it's not linear. I would suggest a 'matched' set, for starters.

You will get a lot of opinion on who should supply the springs, but I will say this: use a company that lists the tolerance range, and that range should be less than 10%, really, less than 5%, but that narrows it down to like 3 or 4 manufacturers.

My personal preference is Global West, but you have to call and talk to tech, let them know what you want, and have them recommend a set. If you don't like them they will exchange for free. (as long as there's no visible damage)

Make sure you comment it's a convertible, the rear weight is slightly more than a hardtop due to the top frame and bracing.

If you are using something other than OE type control arm bushings, mention that too, it matters. A lot.

Keep in mind that due to your current ride height, you can't use that as a reference for amount of drop. But 1.5-2" is probably going to be about right for something that has a little rake and won't bottom out.


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[MPKind]

I upgraded the entire suspension on my ‘65 Catalina last fall. It was costly and quite the experience to get it right.

The major issue was the rear springs.

First 65-6 rears are unique to those 2 years and Pontiac B Body only.

Second, very few manufacturers or suppliers have them.

Third, most sell the HD 140 lbs/in rears, which were standard in the longer WB (Bonneville, Star Chief).

If you buy from Eaton Detroit, ESPO, or PY they will be HD rears. Sounds great until you connect the shocks and discover they’re now too short to provide ample shock extension. That can be solved by getting. Long shocks. 24” extended works. Monroe makes them and others. Less than 22” they will top out.

The upside is the stance is improved the downside is you’re changing static pinion angle and control arm angles. That may or may not cause vibrations from the U joints.

Found only one mfr. that can make the original 122 lb/in standard rate springs.

Coil Spring Specialties in Kansas.


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[HWYSTR455]

Yeah, Coil Spring Specialties states they 'calibrate' the springs, which I don't think means what people think. I bet their' tolerance is still 10% or more.

Taller springs (free height) don't really change your pinion angle measurement, but it might change a little through the entire sweep of travel but shouldn't have a negative effect.

Longer shock stroke? That doesn't sound right either. But, if a spring is too tall, that could be. And suspect the wagon spring is just that, since it's the wrong application.

Like I mentioned before Global West does make 65-66 springs, I suggest calling them. They don't list everything on their' website, but the springs they use are <5% tolerance.

Classic Industries lists springs for the 65-66 B-Body (impala), and they list Global West springs, as well as a number of other manufacturers that make specific springs:

https://www.classicindustries.com/sh...coil%20springs

Here's the Global West listing they have for the B-Body:

https://www.globalwest.net/impala-19...uspension.html

I don't particularly trust Classic Industries, I have in the past gotten wrong parts from them, so I still suggest calling Global West.

If you get a 'stock height' rear spring, and do a 1.5-2" drop in the front, it should work out good. Again, I suggest calling.



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[Redpiston]

Thanks for the info. Gives me lots to think about. Coil Spring Spec is in St Marys. Only about 100 miles from KC. I could them while Im back home. The more I have been looking at it., I think I just want to lower the front. The rear fender lip sits right at the edge of the rim. I have something loose in the front end that seems to make noise on rotation . When rolling slow no noise. But starts knocking as you speed up. Got to get the front wheels off to see what I find.

Anyone out in the Richland WA area?

[HWYSTR455]

If you want to try to see what it would look like lowered, just cut a half a coil off the front springs.



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[MPKind]

Originally Posted by HWYSTR455

Taller springs (free height) don't really change your pinion angle measurement, but it might change a little through the entire sweep of travel but shouldn't have a negative effect.

Longer shock stroke? That doesn't sound right either. But, if a spring is too tall, that could be. And suspect the wagon spring is just that, since it's the wrong application.

Free height is nearly the same for HD and Std springs since the force applied to them will result in similar ride heights, given the proper application per model. HD springs in the shorter WB models (Cat/GP) will result in a taller ride height than how they react in a Bonne/Star Chief. The rear section doesn't really weigh a lot more, it the moment due to the longer car with a longer wheelbase that creates a higher downward force at the axle.

Since the Catalina cannot compress the HD rear coil to the same height as a Bonneville, the shocks have to be longer than the typical extended length shock like the KYBs. I had those in my car and there wasn't much extension left once installed. Why didn't I notice when I installed them? It was a bare chassis with no load, even with the body on it was light since the car wasn't fully assembled and weighted down. Once the car was done, I did note that the rear sat kind of high and didn't settle like I thought it would.

The moral of this is that the springs and shocks must match to provide adequate compression and extension.

Eaton does give you the option of changing the spring ht taller or shorter, you just need to know how that will play out ahead of time. In retrospect, I could've ordered a shorter HD spring that would've worked with the KYB shocks, but I assumed, all stock parts, all is right. It wasn't right. One of the Eaton springs broke on the pigtail from a violent wheel hop episode where the shock was topping out like a slide hammer.

Pinion angle does change when you install taller (installed ht) springs. Also changes the lower control arm angles. This can lead to drive shaft vibration (pinion angle), or if you like to launch your car, the lower arm angles do affect how it hooks, so that's also an issue, but not a deal breaker if you don't race or pound on the car.

[HWYSTR455]

That makes sense, you want the ride height basically centered in the range of full travel of the suspension. But if the range of travel allows going beyond the length of travel a shock allows, it's possible to exceed the length of the shock travel regardless of the spring.

As for the free height comment, as you pointed out, it doesn't have to pertain to the ride height, that's dependent on rate, think that's what I was trying to get at. But honestly, I don't recall what I was thinking at the time I wrote that.

True too on the longer wheelbase, leverage can account for requiring a different spring rate.

I mis-commented on the shock thing too, saying that a taller spring could be a factor, I should have said a higher rate spring. (And at the same free height). That would place the shock longer extended at ride height. But still would think the shock could extend to the range of suspension travel.

OE 4-links do extend past the normal in-service travel of the suspension, hence shock, in order to remove the spring (I guess) for service. But it still could travel past that in-service range in certain conditions, That isn't a bad thing, because the spring could come out if it did. I get if the ride height is close to the end of the range of shock it could 'hammer' the shock into early failure too. Guess maybe it's a safety thing?

I think the real moral to the story is that you need a spring that is basically in the center of the travel range of the suspension at ride height. Doing that would allow use of a 'standard' travel-length shock.

I still say if you use crappy suppliers with poor tolerances you will never get an expected result. And I personally have had issues with Eaton, CCS, and a number of other places that tout 'factory correct spec springs'.

Also, many just lump together applications so they can limit the production runs for savings.

Coil springs are just a particular gauge of 'wire' that are tempered. If you know the values, you can order any spring from someone that has better tolerances and get exactly what you need. Many places make them and they are not very expensive.

Although a Bonnie is longer than a Cat, they are still both B-bodies, like the GP for those 2 years. You should be able to get a spring that works, guessing it would be the rate what matters. 122lbs seems pretty light to me, but not sure what the goal is for the car.


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[MPKind]

Originally Posted by HWYSTR455

I think the real moral to the story is that you need a spring that is basically in the center of the travel range of the suspension at ride height. Doing that would allow use of a 'standard' travel-length shock.

I still say if you use crappy suppliers with poor tolerances you will never get an expected result. And I personally have had issues with Eaton, CCS, and a number of other places that tout 'factory correct spec springs'.

Also, many just lump together applications so they can limit the production runs for savings.

Although a Bonnie is longer than a Cat, they are still both B-bodies, like the GP for those 2 years. You should be able to get a spring that works, guessing it would be the rate what matters. 122lbs seems pretty light to me, but not sure what the goal is for the car.

Yes, the claim of "factory specs" is BS. Clearly I mismatched the shock/spring combo on my car thinking they'd work and paid dearly for it. Never worked as it should. They make the one HD spring that will work on all P8 cars, yet fail to inform the buyer that the short wheel base cars will set at least an inch higher in the rear due to the lower downward forces on the spring, so put the long 24" Monroes in to cover the extension.

At ride ht, the shock ratio of extension to compression should be about 40/60, but 50/50 is OK too.

When those cars were new, they sat on the low side. Note the tire and wheel coverage on the rear wheel. I've compared a lot of the 65-6 car stances in profile photos and you can tell which cars still have stock rate springs and which have HD. If you see some tire above the top of rim, it's likely an HD spring. Given that Monroes are a popular shock for these cars, it's good odds that was used with the HD spring. I prefer that it set higher than stock, they look kind of dumpy when they're that low with 14" wheels.

Factory spring rate specs of 122 and 140 were sourced from the AMA specs for the '65 Pontiac that they provided in the PHS packet. The parts catalog lists several more rear springs, but that's another story.

[HWYSTR455]

If you want to step up to Viking or QA1, they make shocks for different lengths/heights. I think Ridetech does too.

But of course, the premium shocks also have a premium price.

Bilstein lists shocks by size and length, those are around $120ea, much more affordable.


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[MPKind]

Originally Posted by HWYSTR455

If you want to step up to Viking or QA1, they make shocks for different lengths/heights. I think Ridetech does too.

I have Viking shocks on my car along with the PMT Fabrication suspension setup for front and rear. Handles quite well.

Even with the Viking shocks, they spec'd them out for my car at 21.75" extended with the HD springs...too short. I went around and around with the PMT guy about it. He insisted they'd work. ESPO also insisted their springs would be factory ride height...too tall installed. They went so far as claiming that there was something wrong with my car, or it was modified.

After all that I decided to deal with it myself and I called Viking up and told them about it, they have 2" extensions that add extra length to the top of the shock. New extended length 23.75". Better.

[HWYSTR455]

Sweet, know it's tough finding suspension parts for those cars!

Got a pic of stance?

I will dig and see if I can find springs that would work, sure they are out there.

You did the hybrid coilover type on the front?


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[MPKind]

I'll post some new pics soon. Been fighting with the choke lately, I think I got it dialed in finally.

Viking adjustable coil overs in front and regular shocks in the rear. Dual adjustable valves on all.

PMT is the only place currently fabricating parts for B Body cars. I believe RARE did a rear set, but not anymore. You can actually tune the suspension on this thing now...not that I'd know how to do it.

[HWYSTR455]

On my QA1 shocks, double adjustable, I dialed both knobs to lowest setting and started there.

I would go 4 clicks on one knob, starting in the back, feel the diff, and then do the other knob.

Did same in front.

Ride height, you technically need corner scales to do it 'right' but start with a slight rake to the front.

Depending on the car, in order to get 'proper' corner weights dialed in, it could end up with a rake towards the rear. Hence why it's possible the factory had cars that were raked that way.

If you have adjustable end links on your front sway bar, basic rule of thumb is the bar ends should be parallel to the ground. That obviously would change as the ride height moves up & down with adjustments.

In some cases, you can load one side slightly more than another, if corner weights are off after driver/passenger/load weights are added. In some drag apps, some load the passenger side to help with even wheel lift.

Rear in most cases are fixed end links.

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